Foam bodies are used as a seal material which seals a peripheral part of a component and a chassis which requires protection from a gas or a liquid, and a cushioning material which damps vibration and impact, in many fields including fields of architecture, civil engineering construction, electric appliances, electronics and vehicles.
Foam bodies are obtained by a treatment such as blowing of a resin composition mainly comprising an olefin resin and an elastomer. Examples of these foam bodies include foam bodies of thermoplastic resins such as a polyethylene resin and a polypropylene resin, and foam bodies of rubbers such as a synthetic rubber and a natural rubber, and so forth.
When a foam body is used as a seal material or a cushioning material, several characteristics are required, including that compression flexibility of a foam body, that is, the repulsive stream of a foam body to recover from compressed state, is arranged appropriately in accordance with quality of a material of a good in which the said foam body is used and with a use condition thereof; and that the thus arranged repulsive stress and a seal performance are kept during a usable period of a good in which the foam body is used.
In recent years, downsizing of a device has markedly advanced in an electronics field. In a small electronic device having a display area such as a mobile phone, the ratio of the display area to the main chassis surface is desired as large as possible. Because of this, thickness required to a foam body to be disposed between a display panel and a chassis (in a clearance) tends to be thinner than ever and the width thereof tends to be narrower as well.
As one example of a foam body arrangeable under the restriction of such a narrow clearance, a foam body is proposed in which the impact resistance is improved by making its density 0.01 to 0.20 g/cm3 and its average foam cell diameter 10 to 65 μm, and the thickness of the foam body is made to be 0.1 to 1.0 mm (see Patent Literature 1). It is constructed that the foam body is arrangeable even in a narrow clearance of 0.1 to 1.0 (inclusive).